Need more radiator for GT6

In reply to aribert: You'd be surprised at the real source of problems. Often it's something overlooked that doesn't seem like it could be an issue.. Often I've found overheating issues to be ignition related.. a distributor that doesn't have the proper advance. (simple to check for, with the engine off grab the rotor and see if it rotates smoothly indicating it probably has the proper advance)

Check too if the fuel mixture is rich enough. With new oxygenated fuel that leans out the mixture a little lean can be a lot too lean.

Finally all duct work should be in front of the radiator. That will force cool air into the radiator rather than around the radiator. The simplest way is make cardboard templates with a scissors and tape before you transfer the final product into aluminum.

Duct work after the radiator just traps hot air around the engine making problems worse..

aribert wrote: GameBoy - the 3 row, 3 pass back to front cooling path rad that you speak of - are these custom fabb'ed or something available "off the shelf"?

They're available off the shelf, but not for the GT6 specifically, you'll need to "make something fit." CSF makes them for a few models, Allstar has some as well.

On the fabrication side of things, you can convert any 3-row 1-pass radiator with the inlet and outlet at opposite ends into this configuration just by welding/soldering in 2 sheet metal fluid guides. It's not much more work than a regular recore.

A few people have mentioned the ducting after the radiator and the possible lack of an exit path for radiator exhaust air, that's a good point.

if he wanted to redo the radiator mounting. A Nissan Z31 style radiator that lays down infront of the engine would allow a larger surface area and possibly make for an easier time of ducting it to the front grill, which is tiny really, for a car with the GT6's engine size

In response to some suggestions, today I finally got the chance to drive the GT6 w/ both the T-stat removed and with a plate in front of the rad so that air that passes thru the grille has to pass thru the rad and not under it. http://i290.photobucket.com/albums/ll272/aribert/Triumph/lower%20closeout%20in%20frt%20of%20rad%202_zpscjbcfwpz.jpg http://i290.photobucket.com/albums/ll272/aribert/Triumph/lower%20closeout%20in%20frt%20of%20rad_zpsthuraces.jpg

Executive summary - no improvement. Air temp was 55F, I drove several miles on surface streets w/ the elect fan on, entered the freeway and after traveling a mile, I shut the fan off. Slowly the water temp began to rise. When I turned the fan off, the water temp was in the 175F range and after 6 miles the temp was in the 205F range. I turned the fan back on as I exited the freeway to avoid boil over and did a turn around and returned on the freeway, now starting off w/ water temps in the 195 range. Temp continued to climb till the needle was just kissing the edge of the red mark after 6 miles and I turned the fan back on. When the coolant rises in temp when the car is being driven at a steady state 75 mph (and when the air temp is only 55F), I am convinced that it is a radiator cooling or cooling capacity issue.

the fact that the fan cooled it down at highway speeds means that not enough air is going through the radiator. at 50+mph the fans pull should be LOWER than the air going through the radiator.

A study by Lockheed a few years back concluded that a fan (Puller) reaches Max Ability when The shroud Ends at the Midway point of the Fan, many are farther Enveloped for saftey reasons,Aka Fingers, also a shroud Needs to be 360* around the fan.

18 deg.advance at Idle is a Bunch, try going to 12-10 deg. and correct Idle speed with the Carbs. Lots of time people try to get the Max timing at the High RPM (3000) at the expence of Low speed advance and that is an Issue with the correct Curve and or amount it is able to acieve.

Have you verified that the temp gauge is correct? Bring it up to temp, point an infrared pyrometer at the area where the sender is and compare. Also point at the radiator when it's running to look for cold spots.

I'm probably the last guy on the forum to ask about stuff like this, but I'm wondering if there's something in the cooling system that's blocking the water flow. Did someone stuff a rag in a hose when you changing radiators, or is it possible some crud is blocking the flow in the block?

Is it possible to see in the rad with the car running to verify that the coolant is flowing.

Can you drive the car with the hood removed? And if so is the ducting in the ground still intact l? If so try testing with out the hood on the car and see if anything changes. Particularly on the highway.

aribert wrote: Greetings all: My '71 GT6 back in stock form never had a cooling problem - even when stuck in a 45 min stop & go on a hot summer day. But I upgraded to a slightly warmed over 2.5L TR6/TVR engine and upgraded the radiator core from stock 3 row core to a high efficiency 5 row core.

That was a downgrade, not an upgrade. "High efficiency" cores often present a much higher airflow restriction and move less air through them. Likewise, more rows of cooling tubes often hurts cooling because the delta temperature at the rows closest to the engine is so low that you don't extract much heat, so you end up sending hot water right back through the engine. With copper tubes, three is about the limit before you're introducing more liability than gains. With aluminum, there isn't much point going beyond a single row.

Less rows, more airflow, faster coolant, you will cool that engine down.

also the fan needs to pull from the entire Radiator not just the area of the fan.so your shroud should cover the entire Radiator.

Thank you all for the responses. Responding backwards in time:

GTXVette: My fan/shroud covers the entire core: http://i290.photobucket.com/albums/ll272/aribert/Triumph/IMAG0727_zps9421d871.jpg Knurled: I believe you are correct in that my current rad core ended up being a down grade performance wise. My only thought at the moment is am I willing to have the rad recored (will that get me to where I need to be cooling capacity wise) or buy a completely different rad (and all the fabrication involved, with a leaned back cross flow, in addition to supporting the rad, the shrouds need to be remade) - hence the original question about the cross flow Scirraco / ProStreet radiators. I have another GT6 rad, still has the original OEM core, I used it to test acid washing the insides of the rad to remove any potential scale that might have formed - it appeared to pass the test w/o springing a leak (statically, have not had it under pressure) - that spare rad is missing the mtg straps so I need to either find them or unsolder the ones from my existing rad to try it out. Dean1484: Yes I have looked into the rad fill and seen coolant flow when the t-stat opened. Not likely that I will be removing the bonnet anytime soon - I am a one man band and I would need to rig up an overhead lift. stroker: rag or similar I am confident is not the issue - I have never stuffed anything into a hose - I drain first. As to blockage in the engine - I have no history with the engine prior to dismantling it, sending it off to be bored (and tanked) and rebuilding (that was 18 or so years ago). I did remove all freeze plugs and would have removed any visible crud prior to sending it off the the machine shop. In hind sight I deeply regret not keeping the 2L block that I had several years of history with and rebuilding it into a 2.5L. GTXVette: I too have heard that the optimum shroud extends to the for/aft center of teh fan blades. I'll need to look at the current elect fan to see where the shroud ends. I could always carve the shroud back provided I leave stock for the structure supporting the fan motor. As to timing, I have played w/ timing from about 8 deg BTDC to 22 deg BTDC. Also w/ three different distributors (current dist was recurved to the engine package) no noticeable difference (temp/engine cooling) between any of them. DrHess: I used a K-type thermocouple on the rad inlet (after the t-stat): http://i290.photobucket.com/albums/ll272/aribert/Triumph/gage%20reading_zpsmsyo1ftg.jpg I do have a (cheap, Harbor Freight) IR thermometer, I do not trust it much for absolute readings (hence the use of the T-couple) but do use it for relative readings and I see no cool(er) spots in the rad. The top of the rad (inlet)is warmer that the bottom (outlet), off hand I do not remember the temp difference.
madmachine: at freeway speeds the fan should be redundant and as I understand it on a properly functioning system is redundant at air speeds above 30 to 40 mph. That is why I am focusing on freeway speeds - if I avoid rush hour, I can control the speed and make the test reasonably repeatable - I can't do the same on surface streets and there is no hope of driving more that a few miles at most w/o the elect fan being turned on.

How certain are you about the jetting on the Webers? If they are running lean, it could be causing extra heat that can't be dissipated. With a TR6, we found that running slightly rich worked best, but this also led to gas accumulating in the oil.

Initial timing doesn't tell much unless you know the advance curve, you need to know your "all in" mechanical advance which will also confirm the mechanical advance is working properly. Did you try a confirmed working vacuum advance can?

JoeTR6:

I monitor and adjust jetting using a wide band O2 sensor

BrokenYugo:

No ported vac signal from Weber DCOEs. When I had the distributor reconditioned / recurved, this was taken into account and the can mtg point was blanked off. Don't know the rpm of max advance for this distributor. Using a setback timing light I did plot the curve of the previous distributor - don't have that readily available.

Hello, I have the same issues with the same extra horsepower. I have only fought mine for 3 years. Same questions, all new equipment, engine, radiator, etc. Same 5 row radiator that is too dense to allow air flow. I have the same conclusion. More surface area and less rows in the core. Probably cross flow needed. This winter I will make the changes. Best of luck. Any questions I can try to help. Sure is a blast to drive a rotoflex Gt6 convertible with lots of power that is all Triumph!